title: Recent findings in understanding the biological function of vitamin K.
abstract: Vitamin K is required for the posttranslational modification of liver precursors of prothrombin, blood coagulation Factors VII, IX, and X and additional proteins of undetermined functions in plasma and other tissues. This modification involves the formation of gamma-carboxyglutamic acid, an acidic amino acid needed for the interaction of these proteins with calcium ions. The vitamin is a cofactor of a unique microsomal carboxylase which requires the reduced form of vitamin K, CO2, and molecular oxygen. The vitamin is apparently oxidized to its 2,3-epoxide during the carboxylation reaction. Liver microsomes also contain an enzyme which catalyzes the reduction of the epoxide to the vitamin, vitamin K epoxide reductase, and a number of vitamin K reductases. The epoxide reductase appears to be the site of the anticoagulant action of 4-hydroxycoumarins, commonly used as oral anticoagulants.
mesh_terms: D015055:1-Carboxyglutamic Acid / Q000096:biosynthesis; D015110:4-Hydroxycoumarins / Q000494:pharmacology; D000818:Animals; D001779:Blood Coagulation Factors / Q000096:biosynthesis; D002245:Carbon Dioxide / Q000378:metabolism; D019735:Carbon-Carbon Ligases; D002417:Cattle; D055598:Chemical Phenomena; D002621:Chemistry; D008025:Ligases / Q000037:antagonists & inhibitors / Q000378:metabolism; D008862:Microsomes, Liver / Q000378:metabolism; D006899:Mixed Function Oxygenases / Q000378:metabolism; D008954:Models, Biological; D011516:Prothrombin / Q000378:metabolism; D051381:Rats; D014812:Vitamin K / Q000378:metabolism / Q000502:physiology*; D064417:Vitamin K Epoxide Reductases
chemical_list: D015110:4-Hydroxycoumarins; D001779:Blood Coagulation Factors; D014812:Vitamin K; D002245:Carbon Dioxide; D015055:1-Carboxyglutamic Acid; D011516:Prothrombin; D006899:Mixed Function Oxygenases; D064417:Vitamin K Epoxide Reductases; D008025:Ligases; D019735:Carbon-Carbon Ligases; C020660:glutamyl carboxylase